Development Of Silicon-carbon Composite Lithium Battery Cathode Materials

In this paper,artificial graphite electrode scrap is used as the carbon source and micron silicon as the silicon source.Simple compounding was carried out by ball milling to explore the optimal process parameters and optimal silicon doping ratio for ball milling compounding.The composite was then modified with medium temperature asphalt using a precoating and secondary granulation process.Firstly,the optimal process parameters for secondary granulation were explored using low-cost artificial graphite electrode scrap.Finally,the precoating secondary granulation process and precoating process were used to prepare the precoating secondary granulation silicon-carbon composites by treating the dust-absorbing powder with micron silicon.The details of the study are as follows:(1)The artificial graphite electrode scrap is used as a carbon source to compound with micronized silicon by mechanical ball milling.To investigate the effects of ball milling speed and silicon to carbon composite ratio on the physical properties and electrochemical performance of negative electrode materials.After testing and analysis,the ball mill speed of 300r/min and the amount of silicon doping of 10% were determined to be the best experimental conditions.The first charge specific capacity of the Si C composite was 748.6m Ah/g.The first coulometric efficiency was 81.89%.The capacity retention rate after 30 charge/discharge cycles was 54.45%.(2)In order to explore the optimal secondary granulation process parameters,the inexpensive artificial graphite electrode scrap was first selected for the exploration of the optimal secondary granulation process parameters.The optimal asphalt percentage for secondary granulation was determined to be 15%,the optimal bonding temperature to be170°C,and the optimal bonding time to be 2h.The first charge specific capacity of the obtained secondary granulation artificial graphite anode material was 413.9m Ah/g,the first coulomb efficiency was 82.03%,and the capacity retention rate was 84.5% after 30charge/discharge cycles.The secondary granulation silicon-carbon composites were prepared by secondary granulation process using optimal secondary granulation process parameters.The test found that the first charge specific capacity was 749.7m Ah/g when the asphalt ratio was 15%,and the capacity retention rate was 61.83% after 30charge/discharge cycles.When the asphalt ratio was 21%,the first discharge specific capacity was 694.1m Ah/g,and the battery capacity retention rate was 66.03% after 30charge/discharge cycles.It was found through experimental analysis that when the percentage of asphalt in the preparation of secondary granulation silica-carbon composites was increased.The specific capacity of the composites decreased but the cycling performance was improved.The specific volume of the material increases but the circulation performance decreases when the percentage of asphalt is reduced.In order to balance the high capacity and cycling performance of the composite,the silicon was pretreated using a precoating method.Combined with a 15% asphalt percentage for secondary granulation.The secondary granulated silicon-carbon composites with different precoating ratios were obtained.After testing and analysis,the best experimental condition is to use the phenolic resin with the best silicon doping mass ratio of 0.2 for precoating.The obtained secondary granulated silicon-carbon composites had a first charge specific capacity of758.7m Ah/g,a first coulomb efficiency of 85.5%,and a capacity retention rate of 77.76%after 30 charge/discharge cycles.